Deflecting the sun to fight climate change could trigger droughts and hurricanes, the Royal Society has warned.

In a new report, experts argued solar radiation modification (SRM) could reduce global temperatures but “worsen rather than ease” climate change and make the sky look less blue.

In May, the Government’s Advanced Research and Invention Agency (Aria) announced £56.8m for 21 “climate cooling” projects, which include injecting aerosols into the sky to reflect sunlight away from Earth.

However, the report found there were “major uncertainties” and argued the plan may have devastating knock-on effects, particularly if deployed by rogue groups.

Prof Jim Haywood, of atmospheric science at the University of Exeter, said: “What you do in one place can cause climate change in a different place.

“Stratospheric aerosol injection deployment in the northern hemisphere could impact the position of the tropical monsoon and lead to droughts in sub-Saharan Africa.

“Everyone there relies on subsistence farming, so it quickly devastates if there is a drought there.

“In the southern hemisphere, it could lead to an increase in North Atlantic hurricane frequency and intensity, it could lead to winter droughts over the Mediterranean and the Iberian Peninsula.”

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The report authors warned that marine cloud brightening – in which seawater droplets are fired into the air to make marine clouds whiter and more reflective – could lead to dieback in the Amazon, and trigger a “mega La Niña”.

The La Niña climate phenomenon brings cooling of sea surface temperatures in the equatorial Pacific Ocean, altering the jet stream and increasing hurricane activity.

A “termination effect” whereby sun dimming technology was suddenly stopped, could also lead to rapid warming of up to 2C in decades, and cause devastating effects for ecosystems which could not adapt to higher temperatures in time, the report warns.

“These are cautionary tales,” added Prof Haywood. “You can do it badly.”

“It has to be globally coordinated and you would not want it to be done by a single rogue actor.”

Under plans by Aria, five outdoor field trials of climate cooling projects have been proposed, including shooting plumes of seawater spray into the sky to see if it can enhance the reflectivity of low-lying clouds.

The University of Reading has also been given funding to research whether releasing electric charge into clouds could help increase their reflectivity and bounce back sunlight.

Experiments will also be taking place in Canada to find out if it is possible to thicken Arctic sea ice.

Volcanic eruptions have proven that injecting particles in the air can have a large-scale cooling effect, and some scientists believe mass geo-engineering projects are the only solution to bring down temperatures rapidly.

However, others have labelled such schemes as risky and unprovable, with the potential to do more harm than good.

Climate models suggest that between eight and 16 million tonnes of sulphur dioxide would need to be added to the atmosphere each year to achieve one degree of global cooling – about 10 per cent of the pollution emitted globally during peak emissions in the 1980s and 1990s.

The Royal Society report concluded that solar radiation modification could never be used as a main policy response to climate change as it would only mask the effects of emissions.

Prof Sheila Rowan, the director of the Institute for Gravitational Research at the University of Glasgow, said: “Major uncertainties remain including how much cooling could achieve and how the climate would change regionally.

“Solar radiation modification could worsen rather than ease some climate impacts of global warming particularly at a regional level.

“Unilateral action by individual nationals could cause serious regional impacts for others.”

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